Recent years have seen the application of disk drives such as hard disk drives, not only to computers, but also to other areas including home electronic appliances. As a result, quietness during operation of the hard disk drive is increasingly being demanded.
Incidentally, disk drives are liable to generate noise particularly due to the vibration caused by the rotation of a spindle motor during the rotational acceleration (during so-called spinup) caused by the fact that the recording disk is accelerated from a standstill to a predetermined rotational speed by the spindle motor. More specifically, when the recording disk begins to rotate from a standstill, friction acting on a rotation mechanism changes. This leads to unstable rotation, thus resulting in a greater likelihood of noise generation. Further, in a certain rotational speed range, the vibration caused by the spindle motor rotation produces a structural resonance in the disk drive, resulting in a greater likelihood of noise generation.
Japanese Laid-Open Patent No. 1998-172231 (“Patent Document 1”) discloses a technique of generating a rotational frequency waveform of a spindle and controlling the spindle rotation in response to the rotational speed obtained from the generated waveform. On the other hand, Japanese Laid-Open Patent No. 2002-300793 (“Patent Document 2”) discloses a technique of changing the spindle drive control when priority is given to low noise. However, no mention is made with respect to measures to make spinup quieter.